[PO-B2] Poster Session 2

[P2-07] Diffusion behavior and temperature dependence of hydrogen in tungsten and molybdenum under isotropic strain state

^○QuanFu Han¹, Yue-Lin Liu², Ying Zhang¹, Guang-Hong Lu¹ (1.Beihang University, China, 2.Yantai University, China)

The interaction between hydrogen and metal exhibits a great scientific and technological importance so that it has a direct impact on the design and operation of metallic materials. Here, we have carried out first-principles calculations to investigate interstitial hydrogen diffusion behaviors in tungsten and molybdenum by considering double effects of temperature and strain. The temperature and strain effects are reflected by the vibration Helmholtz free energy in the quasi-harmonic approximation and isotropic loading, respectively. The hydrogen diffusion is analyzed through two nearest neighbor tetrahedral sites. At a ground state (0-K) condition, the hydrogen diffusion activation energy can increase and decrease notably with rising compressive and tensile strain, respectively. While at each compressive/tensile strain case, the hydrogen diffusion activation energy depends distinctly on the temperature and increases with rising temperature. This is mainly originated from the contribution of vibration Helmholtz free energy induced by the larger vibration frequency of hydrogen in two metals. With the increasing temperature, the hydrogen diffusivity is shown to be dependent on the compressive/tensile strain alteration. The present study demonstrates a remarkable influence of “temperature and strain” on the hydrogen diffusion behaviors in tungsten and molybdenum.